My first reaction whenever this question is polled is commiseration with The One, because, believe it or not, there is something worse election-wise for an American politician to be than Muslim. Anyway, the raw data:

It’s tempting to blame the change on the uproar over the Ground Zero mosque, but the poll was concluded on August 5 and that story didn’t break big until Obama weighed in on it last week, on August 13. DrewM is surely right that the uptick here is due in part to an unpopular president being lumped in with an unpopular group, but I think it’s broader than that. Note that the change in the number of those who no longer say O is a Christian is twice as large as the number who insist he’s a Muslim; that’s evidence, I think, of Americans feeling so alienated by his policies that they’ve concluded he must be from a different planet culturally — if not Muslim, then at least certainly not Christian. In other words, whatever group he’s in, it ain’t theirs. (Pew missed a big opportunity here in not polling the atheism question, as I bet you’d see an uptick in that too.) As for why he’s so often accused of being Muslim, the default lefty explanation is of course racism but I think it’s more a combination of his middle name, his background growing up in Indonesia, and his attempt to win over Muslim public opinion with his Cairo speech last year. And all of that gets compounded by soundbites that are taken out of context or cleverly edited to make it sound like he’s making admissions about his “true faith.” Just last week a commenter e-mailed claiming that Obama had once told Stephanopoulos that he was a Muslim and I had to send him the link to this post from two years ago to set him right.

It’s all very lame and obnoxious, especially given the testimony from pastors that Obama takes his Christian faith seriously, but much like the Birther thing, there’s virtually nothing you can say to convince someone who’s sure that O is what he thinks he is. I recommend re-reading Karl’s post from earlier this month on the phenomenon of polling Birthers, as it holds plenty of applicable wisdom in this case too. Essentially, when polling people who dislike candidate X, the specifics of the questions are almost irrelevant. As long as they’re negatively inclined — e.g., “Is Obama a werewolf?” — you’ll get a certain core percentage willing to say yes. The news in this poll is that as much as 18 percent think being a Muslim is inherently negative. But as I said above, that’s also true (if not more true) of atheism. Via Mediaite, here’s KP on the issue: